1. Technical Field of the Invention
The present invention relates generally to a fuel injector which may be employed in injecting fuel into an internal combustion engine, and more particularly to such a fuel injector which is equipped with a fuel pressure sensing mechanism secured integrally with a body of the fuel injector.
2. Background Art
Japanese Patent First Publication No. 2007-231770 discloses a common rail fuel injection system equipped with a pressure sensor working to measure the pressure of fuel to be injected into an internal combustion engine. The pressure sensor is installed in an end of a common rail to measure the pressure of fuel stored in the common rail. Typical fuel injectors for use in such a common rail injection system are taught in, for example, Japanese Patent First Publication Nos. 2007-270822 and 2007-218249.
Japanese Patent First Publication No. 57-5526 discloses a fuel injector in which a pressure sensor is installed. The fuel injector has a fuel flow path extending therein and a recess formed near the fuel flow path. The pressure sensor made of a strain gauge is affixed to the recess to measure a change in pressure of the fuel in the fuel flow path which has arisen from the spraying of the fuel from the fuel injector.
The systems taught in the above first to third publications, however, have a difficulty in determining the pressure of fuel supplied to each fuel injector.
The fuel injector, as taught in the above fourth publication, has the recess formed in an outer wall thereof near a lower portion of the fuel flow path. The pressure sensor is, as described above, provided in the recess. The fuel flow path is so formed as to extend through an injector body in an axial direction thereof. The formation of the recess is usually achieved by grinding the outer wall of the injector body. It is, therefore, difficult to control the thickness of the bottom wall (i.e., a diaphragm) of the recess precisely, which may result in a decrease in accuracy in determining the pressure of fuel or a change in pressure of the fuel. Fuel injectors, such as the ones in the first to third publications, designed to spray the fuel at high pressures are generally needed to have an injector body made of a high-hardness metal or an increased thickness of the wall of the fuel flow path in order to withstand the high-pressure fuel and thus have a pronounced problem with the difficulty in controlling the thickness of the diaphragm, in other words, ensuring a desired accuracy in measuring the pressure of fuel in the fuel injector.